The ring of steel is believed to be the best way to protect the heart of London's financial district.

London's first ring of steel was a response to IRA bombs in the Baltic Exchange in Bishopsgate in 1992.

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The Gherkin building now stands on the site of the Baltic Exchange which was bombed by the IRA in the 1990s

It would be the first time since the late 1990s that manned checkpoints were used.

Such checkpoints were phased out after the IRA announced a ceasefire in 1994.

The new protective ring will border Liverpool Street, the Bank of England and Fenchurch Street - an area which is home to some of the capital's newest and most recognisable skyscrapers.

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Crash-proof barricades are one of the measures suggested in the report

"This eastern section of the City of London is especially of importance in as much as there are going to be a number of major landmarks developed around the area that could be of interest," the report said.

The new plan would be subject to a consultation but could be fully implemented by 2022.

Will Geddes, founder of International Corporate Protection said: "Although we've seen of late 'lo-fi type' attacks, like the Berlin Christmas market where a lorry that was hijacked and driven into a crowded area, we cannot discount the type of attack that will... include a large truck packed with explosives"